There is an inkjet printer in which an ink is ejected from nozzles (ink ejection ports), and plural ink droplets are successively ejected from one nozzle in order to form one pixel. JP-A-9-66603 discloses an ink ejection device (inkjet printer), in which two ink droplets are successively ejected and the later ejected ink droplet is merged with the initially ejected ink droplet before the ink droplets reach a sheet face. The merged ink droplet then reaches the sheet face. In order to enable the two ink droplets to merge before reaching the sheet face, two pulse signals having a pulse width equal to a propagate time period (AL) and different voltages are applied at a time interval of 2.5AL. Alternatively, two pulse signals which have pulse widths of 0.5AL and AL, respectively, having the same voltage are applied at a time interval of 2.5AL. Here, the propagate time period AL represents a time required for a pressure wave generated in the ink filling the ink channel to the other end of the ink channel in a lengthwise direction of the ink channel.